• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.11a
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• pp.33-37
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• 2002

본 연구에서는 전해도금법을 이용하여 플립칩용 Ni, Ni-Cu 합금 UBM (Under Bump Metallurgy) 및 Sn-Ag 무연 솔더 범프를 형성하였다. 솔더 범프의 전해도금시 고속도금 방법으로 균일한 범프 높이를 갖도록 하는 도금 조건 및 도금 기판의 역할로서의 UBM의 영향을 조사하였다. Cu/Ni-Cu 합금/Cu UBM을 적용한 경우 음극시편의 전극 접점수를 증가시켰을 때 비교적 균일한 솔더 범프를 형성시킬 수 있었던 반면, Ni UBM의 경우는 접점수를 증가시켜도 다소 불균일한 솔더 범프를 형성하였다. 리플로 시간을 변화하여 범프 전단 강도 및 파단 특성을 조사하였는데 Ni UBM의 경우 Cu/Ni-Cu 합금/Cu UBM에 비해 전단강도가 다소 낮은 값을 가졌고 금속막이 웨이퍼에서 분리되는 파괴 거동이 관찰되었다.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.68-71
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• 2003

The reaction of ultra-small eutectic 58Bl-42Sn solder bump with Au/Ni/Ti and Au/Cu/Ti UBMs during reflow was studied. The eutectic Bi-Sn solder bumps of $46{\mu}m$ diameter were fabricated by using the evaporation method and were reflowed using the rapid thermal annealing system. The intermetallic compound was characterized using a SEM, an EDS, and an XRD. The $(Cu_xAu_{1-x})_6Sn_5$ compounds formed at the interface between Bi-Sn solder and Au/Cu/Ti UBM. On the other hand, in the Bi-Sn solder bump on Au/Ni/Ti UBM, the faceted and rectangular intermetallic compounds were observed on the solder bump surface and inside the solder bump as well as at the UBM interface. These intermetallic compounds were Identified as $(Au_{l-x-y}Bi_xNi_y)Sn_2$ phase.

• Proceedings of the KWS Conference
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• 2002.05a
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• pp.276-277
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• 2002

• Journal of the Microelectronics and Packaging Society
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• v.11 no.4 s.33
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• pp.43-48
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• 2004

Electromigration of Sn-3.5Ag-0.5Cu solder bumps was investigated with current densities of $3{\~}4{\times}10^4 A/cm^2$ at temperatures of $130{\~}160^{\circ}C$ using flip chip specimens which consisted of upper Si chip and lower Si substrate. Electromigration failure of the Sn-3.5Ag-0.5Cu solder bump occurred with complete consumption of Cu UBM and void formation at cathode side of the solder bump. The activation energies for electromigration of the Sn-3.5Ag-0.5Cu solder bump were measured as 0.61 eV at current density of $3{\times}10^4 A/cm^2$, 0.63 eV at $3.5{\times}10^4 A/cm^2$, and 0.77 eV at $4{\times}10^4 A/cm^2$, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.1
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• pp.35-42
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• 2024

Recently, with the miniaturization and high integration of semiconductor chips, the bump bridge phenomenon caused by fine pitches is drawing attention as a problem. Accordingly, Cu pillar bump, which can minimize the bump bridge phenomenon, is widely applied in the semiconductor package industry for fine pitch applications. When exposed to a high-temperature environment, the thickness of the intermetallic compound (IMC) formed at the joint interface increases, and at the same time, Kirkendall void is formed and grown inside some IMC/Cu and IMC interfaces. Therefore, it is important to control the excessive growth of IMC and the formation and growth of Kirkendall voids because they weaken the mechanical reliability of the joints. Therefore, in this study, isothermal aging evaluation of Cu pillar bump joints with a CS (Cu+ Sn-1.8Ag Solder) structure was performed and the corresponding results was reported.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.267-271
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• 2004

The joint strength and fracture surface of Sn-Pb solder bump in photo diode packages after isothermal aging testing were studied experimentally. Cu/Sn-Pb solders were adopted, and aged for up to 900 hours at 12$0^{\circ}C$ and 17$0^{\circ}C$ to analyze the effect of intermetallic compound(IMC). In 900-hour aging experiments, the maximum shea strength of Sn-Pb solder decreased by 20％ and 9％. The diffraction patterns of Cu$_{6}$Sn$_{5}$, scallop-shape IMC, and planar-shape Cu$_3$Sn were observed by Transmission Electron Microscopy (TEM).EM).

• Journal of the Microelectronics and Packaging Society
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• v.15 no.2
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• pp.37-45
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• 2008

In this study, reliabilities of Cu (60 um)/SnAg (20 um) double-bump flip chip assemblies were investigated for the flip chip interconnections on organic substrates with 100 um pitch. After multiple reflows at $250^{\circ}C\;and\;280^{\circ}C$, bump contact resistances were almost same regardless of number of reflows and reflow temperature. In the high temperature storage test, there was no bump contact resistance change at $125^{\circ}C$ up to 2000 hours. However, bump contact resistances slightly increased at $150^{\circ}C$ due to Kirkendall voids formation. In the electromigration test, Cu/SnAg double-bump flip chip assemblies showed no electromigration until about 600 hours due to reduced local current density. Finally, in the thermal cycling test, thermal cycling failure mainly occurred at Si chip/Cu column interface which was found out the highest stress concentration site in the finite element analysis. As a result, Al pad was displaced out under thermal cycling. This failure mode was caused by normal compressive strain acting Cu column bumps along perpendicular direction of a Si chip.

• Journal of the Microelectronics and Packaging Society
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• v.5 no.1
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• pp.7-18
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• 1998

In the flip chip interconnection on organic substrates using eutectic Pb/Sn solder bumps highly reliable Under Bump Metallurgy (UBM) is required to maintain adhesion and solder wettability. Various UBM systems such as 1$\mu$m Al/0.2$\mu$m Pd/1$\mu$m Cu, laid under eutectic Pb/Sn solder were investigated with regard to their interfacial reactions and adhesion proper-ties. The effects of numbers of solder reflow and aging time on the growth of intermetallic compounds (IMCs) and on the solder ball shear strength were investigated. Good ball shear strength was obtained with 1$\mu$m Al/0.2$\mu$m Ti/5$\mu$m Cu and 1$\mu$m Al/0.2$\mu$m ni/1$\mu$m Cu even after 4 solder reflows or 7 day aging at 15$0^{\circ}C$. In contrast 1$\mu$m Al/0.2$\mu$m Ti/1$\mu$m Cu and 1$\mu$mAl/0.2$\mu$m Pd/1$\mu$m 쳐 show poor ball shear strength. The decrease of the shear strength was mainly due to the direct contact between solder and nonwettable metal such as Ti and Al resulting in a delamination. In this case thin 1$\mu$m Cu and 0.2$\mu$m Pd diffusion barrier layer were completely consumed by Cu-Sn and pd-Sn reaction.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.85-91
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• 2002

Even though electroless Hi and Sn-Ag-Cu solder are widely used materials in electronic packaging applications, interfacial reactions of the ternary Ni-Cu~Sn system have not been known well because of their complexity. Because the growth of intermetallics at the interface affects reliability of solder joint, the intermetallics in Ni-Cu-Sn system should be identified, and their growth should be investigated. Therefore, in present study, interfacial reactions between electroless Ni UB7f and 95.5Sn-4.0Ag-0.5Cu alloy were investigated focusing on morphology of the IMCs, thermodynamics, and growth kinetics. The IMCs that appear during a reflow and an aging are different each other. In early stage of a reflow, ternary IMC whose composition is Ni$_{22}$Cu$_{29}$Sn$_{49}$ forms firstly. Due to the lack of Cu diffusion, Ni$_{34}$Cu$_{6}$Sn$_{60}$ phase begins growing in a further reflow. Finally, the Ni$_{22}$Cu$_{29}$Sn$_{49}$ IMC grows abnormally and spalls into the molten solder. The transition of the IMCs from Ni$_{22}$Cu$_{29}$Sn$_{49}$ to Ni$_{34}$Cu$_{6}$Sn$_{60}$ was observed at a specific temperature. From the measurement of activation energy of each IMC, growth kinetics was discussed. In contrast to the reflow, three kinds of IMCs (Ni$_{22}$Cu$_{29}$Sn$_{49}$, Ni$_{20}$Cu$_{28}$Au$_{5}$, and Ni$_{34}$Cu$_{6}$Sn$_{60}$) were observed in order during an aging. All of the IMCs were well attached on UBM. Au in the quaternary IMC, which originates from immersion Au plating, prevents abnormal growth and separation of the IMC. Growth of each IMC is very dependent to the aging temperature because of its high activation energy. Besides the IMCs at the interface, plate-like Ag3Sn IMC grows as solder bump size inside solder bump. The abnormally grown Ni$_{22}$Cu$_{29}$Sn$_{49}$ and Ag$_3$Sn IMCs can be origins of brittle failure.failure.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.111-119
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• 2005

Stack specimen with three dimensional interconnection structure through Cu via of $75{\mu}m$ diameter, $90{\mu}m$ height and $150{\mu}m$ pitch was successfully fabricated using subsequent processes of via hole formation with Deep RIE (reactive ion etching), Cu via filling with pulse-reverse electroplating, Si thinning with CMP, photolithography, metal film sputtering, Cu/Sn bump formation, and flip chip bonding. Contact resistance of Cu/Sn bump and Cu via resistance could be determined ken the slope of the daisy chain resistance vs the number of bump joints of the flip chip specimen containing Cu via. When flip- chip bonded at $270^{\circ}C$ for 2 minutes, the contact resistance of the Cu/Sn bump joints of $100{\times}100{\mu}m$ size was 6.7m$\Omega$ and the Cu via resistance of $75{\mu}m$ diameter, $90{\mu}m$ height was 2.3m$\Omega$.